Losi LOSB0021 User Manual
Page 9
9
Engine Break-In and Adjustments
The new Losi 3.4 engine in your 810 has been machined to
tight tolerances and does not need an extended break-in.
It is always a good idea to take it easy for the first few tanks
of fuel to let all the gears and moving parts seat into one
another. You will notice after the first hour of operation that
the engine will pick up power. It is highly advised that you use
Nitrotane 20% Sport fuel as the carburetor is factory set for
this fuel and other fuels may require immediate needle valve
adjustments. NEVER use model airplane fuel as it may cause
damage to the engine and void any warranty. If you change
fuels or run in dramatically different environments (hot/cold,
high/low elevation, etc), you will probably have to adjust
at least the high-speed needle to prevent overheating and
maintain proper performance.
Tuning a Nitro Engine
Adjusting the carburetor is one of the most critical facets
of running a nitro-powered RC vehicle. The fuel mixture is
referred to as being “rich” when there is too much fuel and
“lean” when there is not enough fuel for the amount of air
entering the engine. The amount of fuel entering the engine
is adjusted with high- and low-speed threaded needle valves.
The low-speed needle is located in the front of the moving
slide. The high-speed needle sticks straight up at the back
of the carburetor. Both feature a slotted head that is used
as a reference and receptacle for a flat blade screwdriver
for adjustments. The mixture is made richer by turning the
needle counterclockwise and leaner by turning clockwise.
An overly “rich” mixture will yield sluggish acceleration and
performance with thick smoke from the exhaust. A “lean”
mixture can cause the engine to hesitate before accelerating
or, in some cases, to lose power momentarily after the initial
acceleration. A lean mixture also makes the engine run hotter
than desired and does not provide enough lubrication for the
internal engine components, causing premature wear and
damage. It is always advisable to
run the engine slightly
rich
and
never lean
to avoid overheating and possible
damage.
Base Start-up Settings from the Factory
High-Speed Needle—2
1
/
2
turns out from bottom
Low-Speed Needle—2
1
/
2
turns out from bottom
Faster
Slower
Engine Tuning
After the engine is broken in, you can tune it for optimum
performance. When tuning, it is critical that you be cautious
of overheating as severe damage and premature wear can
occur. You want to make all carburetor adjustments in “one
hour” increments.
Leaner
Richer
3
1
2
1= Idle Stop Screw
2=Low-Speed Needle
3=High-Speed Needle